Abstract
Compact, electrically-driven compressors are a core component of a novel active high-lift system for future commercial aircraft. A newly-developed aeromechanical optimization process was used to design the compressor stage. The optimization resulted in an unusual mixed-flow compressor design with very low aspect ratio blades and a high rotational speed of up to 60,000 rpm. Due to the unusual design, experimental validation of the performance predictions by means of CFD is necessary. This paper presents the first experimental results obtained using a preliminary prototype at part-speed, i.e. rotational speeds from 20,000 to 30,000 rpm. The experimentally-determined pressure ratios deviate up to 1.5 %, the polytropic efficiencies up to 4 percentage points from the CFD predictions. Besides the deficiencies of available turbulence models, the underestimation of overall losses is presumably due to the omission of the volute in the CFD model. An experimental validation of the CFD predictions at full-speed is under way.
Highlights
Improved high-lift systems have the potential to reduce noise and carbon dioxide emissions of modern commercial aircraft
This paper presents the first experimental results obtained using a preliminary prototype at part-speed, i.e. rotational speeds from 20,000 to 30,000 rpm
It was demonstrated that using the “cold” geometry for the CFD analysis is acceptable
Summary
Improved high-lift systems have the potential to reduce noise and carbon dioxide emissions of modern commercial aircraft. The use of automatic optimization methods as described by Teichel et al [3] resulted in an unusual, transonic, mixed-flow compressor design with a high axial flow component. According to CFD predictions, the aerodynamic design point (total pressure ratio of 2.33 and corrected mass flow rate of 1.11 kg/s) is reached at a corrected rotational speed of 60,125 rpm with a polytropic efficiency of 83.3 %. Mixed-flow compressors combine advantages of both axial and radial compressors, resulting in compact stages with high specific power. An experimental study of tip clearance effects for a mixed-flow compressor with a high proportion of radial flow was performed by Rajakuma et al [13] for constant and variable tip clearance gaps. For the present compressor an axial slot casing treatment has been designed by Du & Seume [15] and recently experimentally evaluated by Du et al [16]
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